1. Field of the Invention
The invention relates to a gear transmission with stepless adjustable translation ratio for converting rotational speeds and torques between two shafts.
2. Brief Description of the Background of the Invention Including Prior Art
Such converters represented by gear transmissions with stepless adjustable translation are employed in the complete motive power engineering, in particular in connection with machine tools as with vehicle engines.
Such a gear transmission is known as a variation of ratchet gear or ratchet mechanism drives from the German patent 474205. A gear transmission is proposed there, wherein the rotational motion of the drive shaft is transformed by way of several cam disks disposed on the driving shaft into a back and forth motion of push rods and by intermediate positioning of a variable translation device into a back and forth motion of gear racks, wherein the gear racks in the following successively operate on the driven shaft and drive the driven shaft through gear wheels and blocking couplings (free engine clutch). The variable translation device comprises a two armed lever with adjustable hinge point for changing the in each case effective lever lengths and thus also transmission ratio size. The gear racks move with uniform speed during the force transmission phase and are thus able to drive the driven shaft with a uniform angular speed. The motion transfer in the device according U.S. Pat. No. 4,565,105 occurs in a similar way.
A substantial deficiency of such gear transmission systems comprises that the wear appearances occurring during the transforming of the translational motion into a rotational motion of the driven shaft, for example, the back and forth motion of the gear racks to a rotational motion of the gear wheel in the gear rack/gear wheel drive, are of substantial size in particular in continuous operation and can interfere substantially with the reliability of the overall gear transmission. The wear appearances concern in particular those regions of the toothed wheel work of the gear rack and gear wheel, which are subjected more frequently to a particularly large mechanical load during the periodical loading in continuous operation as compared to other regions. However the wear occurring also upon employing cam drive gear mechanisms as a second force transmission means in the regions between engagement members and cam members and their guide tracks or, respectively, between engagement members is not negligible. The non-uniform distribution of the material abrasion by wear based on the non-uniform load of the stroke distance available of the gear rack or, respectively, of the engagement member is further increased in that the force to be transmitted increases, based on the increase of the translation setting (decrease of the length of the stroke distance) under the condition of constant transmission power. The strong and in particular also non-uniform wear at the function determining contact faces of the gear transmission elements of the second force transmission means transferring the motion is, however, associated with deviations from the desired relative motion of the gear transmission means, which in turn are the cause for a rapidly advancing wear process.